[Anal high grade dysplasia associated with Crohn's disease:a case report].

A 47-year-old male patient with anal pain underwent a colonoscopy 12 years after Crohn's disease diagnosis. A biopsy from the protuberance of the anal canal revealed a well-differentiated adenocarcinoma. A reexamination of the histopathological specimen at our hospital revealed anal high grade dysplasia (HGD), thereby changing the initial diagnosis. A distal colon resection and rectal amputation were performed, and the final diagnosis of the resected specimen was anal canal HGD. While HGD associated with Crohn's disease is rare in Japan, this case suggests the importance of endoscopic examination, which might help in early detection of HGD.